Promising treatments have been added to the oncologist's arsenal in recent years. Treatments that, unlike conventional chemotherapy, do not aim to destroy cancer cells directly, but rather activate the patient's own immune system to recognize and attack tumor cells again. This new treatment is called immune checkpoint therapy. This involves administering antibodies (large Y-shaped proteins that can stick to the surface of cells) that remove the brakes from the immune system. The disadvantage of this innovative treatment is that the rejuvenated immune system can also attack cells that we want it not to recognize - our own body's cells. This is called autoimmunity. Patients who receive immune checkpoint therapy may suffer from symptoms such as skin rashes, diarrhea, hepatitis or hypothyroidism. The purpose of this study is to find biomarkers predictive of the development of these side effects, and possibly also predict a better outcome of the cancer therapy. The investigators will also look for the presence of antibodies against the endocrine glands (glands that produce hormones, such as the thyroid, adrenal, pituitary, and pancreas) before the start of the immune therapy.